1. Field of the Invention
The present invention relates generally to semiconductor substrates having thin films of titanium nitride (TiN) deposited thereon by low pressure chemical vapor deposition (LPCVD) methods, and more particularly, to a process for reducing the chlorine content of such TiN films for lessening the resistivity of such films.
2. Description of the Prior Art
It is well known in the semiconductor industry to use thin films of titanium nitride (TiN) as a barrier metal for semiconductor devices. Such thin films of TiN can be deposited using chemical vapor deposition (CVD) techniques. As a barrier metal, such thin films of TiN may be deposited over semiconductor contact areas prior to formation of aluminum contact layers to prevent the aluminum connection layer from directly contacting the underlying semiconductor material, which is most typically silicon. Such TiN films provide good step coverage over the surface of the semiconductor substrate, particularly within submicron contacts. Such TiN films also provide low contact resistance to salicide, low leakage, excellent adhesion to the underlying semiconductor substrate, and high thermal stability. Such TiN films also provide good adhesion for subsequent films of tungsten.
In Sherman, "Growth and Properties of LPCVD Titanium Nitride as a Diffusion Barrier for Silicon Device Technology", J. Electrochem. Soc., Vol. 137, No. 6, June 1990, a process is described for depositing thin films of TiN upon a silicon substrate in a single-wafer cold wall reactor using a low pressure CVD (LPCVD) process.
Accordingly, it is an object of the present invention to provide a process for forming titanium nitride films upon silicon substrates having a decreased sheet resistance.
It is another object of the present invention to provide a process for forming titanium nitride films upon silicon substrates having more uniform sheet resistance.
It is still another object of the present invention to provide a process for forming titanium nitride films upon silicon substrates wherein such titanium nitride films have a decreased chlorine content.
It is yet another object of the present invention to provide such a process which can be performed without substantially altering the flow gases or apparatus commonly used to deposit such titanium nitride films.
These and other objects of the present invention will become more apparent to those skilled in the art as the description thereof proceeds.